Let me make sure I'm understanding what you're asking. If a lead in an engagement program takes an action, you then want to trigger an email message to go to all leads at the company of the lead who took the action. Is that correct?

I think that would be one solution. The other solution would be to have contact one within the company takes and action. Then when contact two in that same company takes an action, we send email(s) referencing them both. Something to the effect of "We noticed both of you....".